Date of Award
Understanding vegetation change is central to forecasting the impacts of climate change. Percent cover, determined from a point frame method, is commonly used to monitor vegetation change. Cover is influenced by canopy structure which may change with the size (growth) or number (density) of individual plants. The overarching objective of this project was to document the relationship between vegetation cover and traits representing plant growth and density and determine if these relationships changed with warming. We used regressions and analysis of covariance to detect which of several traits was most strongly related to cover in vegetation at a wet and a dry site as well as across a grid covering a range of community types in Northern Alaska. The wet and dry sites also included a warming experiment. We found that graminoid cover was positively correlated with proxies for plant growth (canopy height and leaf length) at the wet and dry sites but was negatively correlated with density across the grid. This signified an inverse relationship between growth and density. Shrub cover was not correlated with any of the selected traits at the wet site, but was correlated with inflorescence length and canopy height at the dry site. Across the grid evergreen shrub cover correlated with density while deciduous shrub cover correlated with canopy height. Experimental warming significantly altered the relationships between vegetation traits and cover, particularly at the dry site, resulting in varying relationships between cover and traits in control versus warmed plots. Furthermore, correlations between cover and vegetation traits for growth forms were not always consistent with those of their constituent species. These results demonstrate that cover is related to canopy structure which differs across species and community types, and may change with warming. Continued research at the landscape level is needed to provide a better understanding of the implications of observed changes in plant cover in response to climate warming.
Gregory, Jessica L., "Structural Comparison of Arctic Plant Communities Across the Landscape and with Experimental Warming in Northern Alaska" (2014). Masters Theses. 746.